Psoriasis: clinical presentation, histopathology and differential diagnosis.

Psoriasis Overview

In this section, Dr. Victoria Kozlowska and her fellows discuss psoriasis, focusing on histopathology, clinical presentations, and differential diagnosis.

Clinical Subtypes of Psoriasis

• **** Psoriasis is an immune-mediated disorder involving T cells and various cytokines.

• **** Classic plaque psoriasis presents as well-circumscribed erythematous scaly plaques with features like the Auspitz sign.

• **** Plaque psoriasis can exhibit cabinetrization with a diffuse distribution due to scratching.

• **** Early plaque psoriasis may lack obvious scaling, making clinical diagnosis challenging without biopsy confirmation.

• **** Symmetric plaque psoriasis typically affects areas like elbows, knees, and scalp in a classic distribution pattern.

Other Clinical Presentations

• **** Partially treated plaque psoriasis may appear macerated but still exhibits scaling; consider tinea in the differential diagnosis.

• **** Inverse psoriasis lacks scaling in areas prone to maceration, presenting as shiny erythema; differentiate from other conditions like contact dermatitis.

Further Clinical Presentations of Psoriasis

This section delves into additional clinical presentations of psoriasis beyond the classic plaque form.

Guttate Psoriasis

• **** Guttate psoriasis presents with less developed plaques and follicular involvement; consider streptococcal infection history for diagnosis.

Erythrodermic Psoriasis

• **** Erythrodermic psoriasis manifests as full-body erythema with a broad differential diagnosis including atopic dermatitis and mycosis fungoides. Differentiate based on nail changes and joint involvement.

Ethiopian Psoriasis Pathology and Differential Diagnosis

In this section, the speaker discusses Ethiopian psoriasis pathology, differential diagnoses, and treatment considerations for various psoriasis subtypes.

Ethiopian Psoriasis Pathology

• Ethiopian psoriasis pathology aids in diagnosis.

• Verruca psoriasis presents with well-circumscribed plaques and severe scale.

• Consider pustular psoriasis in patients with sterile pustules on erythematous backgrounds.

• Posture psoriasis differential includes hypocalcemia, infections, medications, and corticosteroids.

Histology of Common Psoriasis Variants

• Classic psoriasis lesion features epidermal acanthosis, perikeratosis mounds, and intraepidermal pustules.

• Guttate psoriasis exhibits hyperkeratosis, papillomatosis, and vessel tortuosity without acanthosis.

• Veruca-like appearance characterizes verrucous psoriasis with hyperkeratosis and intraepidermal pustules.

Differential Diagnosis of Seborrheic Dermatitis vs. Psoriasis

This part delves into distinguishing seborrheic dermatitis from other inflammatory conditions like psoriasis through histological features.

Seborrheic Dermatitis vs. Psoriasis

• Seborrheic dermatitis shows parakeratosis mounds with subtle spongiosis; biopsy aids differentiation.

• Pityriasis rosea differs from psoriasis by more spongiosis; characteristic feature is small parakeratosis mounds above spongiosis.

• Arthropod bites exhibit parakeratosis mounds with serum right above spongiosis; extravasated erythrocytes may not always be present.

Drug-induced Erythema Multiforme vs. Eruptive Pustulosis Psoriasiform

The speaker compares drug-induced erythema multiforme to eruptive pustulosis psoriasiform based on histological findings.

Drug-induced Erythema Multiforme vs. Eruptive Pustulosis Psoriasiform

• Drug-induced erythema multiforme displays more spongiosis and neutrophilic pustules; clinical-pathological correlation is crucial for diagnosis.

Clinical Dermatology Cases Analysis

In this section, various dermatological cases are presented and discussed in detail, focusing on differentiating factors between conditions like hydroid eczema, psoriasis, prurigo, lichen simplex, and nutritional deficiencies.

Hydroid Eczema vs. Psoriasis

• Compact hyperkeratosis with lamina lucida observed in the acral skin.

• Presence of lymphocytes and adjacent spongiosis distinguishes hydroid eczema from psoriasis.

Prurigo vs. Lichen Simplex

• Threshiform acanthosis with compact stratum corneum seen in prurigo compared to psoriasis.

• Features like vertical collagen streaks and hypergranulosis typical for lichen simplex.

Granular Parakeratosis

• Extensive basophilic stratum corneum resembling chronic eczema or psoriasis.

• Location in intertriginous areas without tortuous vessels aids in diagnosis.

Pityriasis Rubra Pilaris

• Differentiating features from psoriasis include alterations in compact parakeratosis and orthokeratosis areas.

Nutritional Deficiency Presentations

• Identification of specific pallor of the epidermis indicating a nutritional deficiency condition.

• Various presentations of nutritional deficiencies ranging from rashes to papules or vesicles emphasized.

Differential Diagnosis: Spongiotic Dermatitis

This segment delves into the challenges of diagnosing spongiotic dermatitis based solely on histopathology due to overlapping features with other conditions like allergic contact dermatitis or drug reactions.

Spongiotic Dermatitis Characteristics

• Extensive spongiosis mimicking subcorneal pustules but identified as Langerhans cells under high power view.

Differential Diagnoses

• Presence of eosinophils suggesting allergic contact dermatitis or insect bite reactions among differential diagnoses.

Detailed Dermatopathology Cases Analysis

In this section, the speaker discusses various dermatopathology cases, highlighting key features and diagnostic considerations.

Prominent Coronoid Lamellae

• More prominent coronoid lamellae observed.

• Characteristic cells at the bottom of the carnot lamella.

• Emanation from the epidermis at a 45-degree angle.

Unusual Guests in Horn Examination

• Not always inflammatory; careful examination required.

• Example of Norwegian scabies with multiple schematic mites.

Clear Cell Acanthoma Diagnosis

• Well-circumscribed lesion with a central pallor.

• Classic example of clear cell acanthoma; easy to misdiagnose as psoriasis without history.

Diagnostic Challenges and Features

• Clear cell differentiation not always apparent; PAS stain may be used for clarification.

• Presence of neutrophils characteristic for clear cell acanthoma.